Electrical transformer



March 26, 1929. W M BAILEY 1,706,837

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.Y UNITED STATESA PATENT OFFICE.A

WILLIAM M. BAILEY, OF LYNN, MASSACHUSETTS, ASSIGNOR T WIRELESS SPECIALTY APPARATUS COMPANY, OF BOSTON, MASSACHUSETTS, A CORPORATION Y0]? NEW YORK.

' ELECTRICAL lTRANSFORMER.

Applicationled December 5, 1922. Serial Ni'oi. 604,990.

' This invention relates to improvements in electrical action of the invention in a trans electrical transformers, particularly for former of the general type of Fig. 6;VV feeble currents such as those employed in Fig. 8 is a diagrammatic illustration of the artof communication by high frequency the primary winding of another form of current, ein connection with amplifiers emmy transformer alternative to those of Figs.

ploying currents at high or low frequencles, 1, 4and v or both. Y j F 1g. 8,a is a diagrammatic illustration of 60 The object of the invention is to improve a prlmary winding of another method of the construction and electrical operation of obtaining the. same .electrical action ofthe 1'0 lauch transformers. transformer of Fig. 8 as is obtained in that of The invention relates 'to the various novel Fig. 8; features and their combination, as herein Fig. 9 is a diagrammatic illustration of disclosed and claimed and the invention has one of my transformers wherein the im- 65 most particular relation to the construction provements are applied to both primary and of transformers employed tocouple the suc- Secondary, each winding resembling that of cessive thermionic tubes of the amplifier re- Flg.. 8. ceiving set. Fig. 1shows a transformer suitable for 70 0f the drawings, f use 1n any transformer-coupled tube set such, Figure 1 is a vertical section in perspecfor example, as that shown in Fig. 3. It i 2e tive of one' of my transformers; 1S most partlcularly adapted for use as radio Fig. 2 is a diagram of the winding thereon frequency transformer (as in Fig. 3 at RTl, which fmore'clearly shows the arrangement RT2 and RT3. In Fig. 1 the transformer thereof; includes a core of iron laminae IL, the in- Fig. 2a is a diagram showing a method d1v1d ual laminae being covered with an inalternative to that of Figs. 1 and 2 for obsulatlng varnish to insulate them from one taining the electrical action of the invention another. These laminae are supported by a infa transformer of the general type of sheet of any suitable insulating material IS Fig 1; (see also Fig. 4), about half the totall of Fig. 3 is a diagram of the circuits of an lamlnae being mounted on the respective amplifier employing transformers of the sldes of the sheet. The laminae IL are held form of Figs. 1, 2 and 2a, with an additional to sheet IS by an enclosure of varnished showing of an arrangement for simultanepaper Over VP is wound the primary ously moving the tores of all the successive coll PR 1n a manner to be described. Over transformers together with compensating prlmary PR is plat-ed a second layer of damping means; Y varmshed paper VP1. Over VPl is wound Fig. 4 is a vertical section in perspective the secondary coil SC of the transformer. of anotherform of transformer involving The resulting transformer is placed in the the invention; circuit of (for example) Fig. 3 in the man- Fig. 4a is a perspective View showing a ner shown; that is, one end of primary PR modified form of support for the type of (an end to be designated later) is connected transformer windings of Fig. 4; y yto the plate of the preceding t-ube as RFl Fig. 5 is a diagram-of the coils which are (radio frequency tube 1), the other end of wound on thepsupport of Fig. 4 for the primary PR is to be connected to the plate transformer of Fig. 4; battery PB (Fig. 3) one end of secondary Fig. 6 is a vertical section of another form SCis to be connected to the grid of a sucof my transformer alternative with that of eeeding tube (asRFz, Fig. 3) and the other Fig. 1 or Fig. 4; end of secondary SC is to be connected to the 100 Fig. 7 is a diagrammatic illustration of grid bias potentiometer, i. e., POT2, Fig. 3. the primary winding of the transformer of Primary PR of the. transformer of Fig. 1

Fig. 6 showing more clearly the. arrangeis wound in the manner shown in Fig. 2. ment thereof; The portion of PR which is connected to Fig. 7a is a diagram showing a method the tube plate is wound say clockwise, and 105 alternative to that of Fig. 7 for obtaining the this portion constitutes a larger part of the mary is wound clockwi entire primary, being shown at the left in Figs. 1 and 2. The remaining portion of primary FR is wound anticloclnvise as shown, this portion being located at the right and start-ing from a point of reversal X. That is, from leftto point X, the pri- :e,- at X the direction of winding is reversed, and from point X to the right the winding Ais anticlockwise.

In'Fig. 2 is shown a inethod alternative to that of I`Figs. l and 2, of obtaining the same electrical action. In Fig. 2L the entire primary PR is wound clockwise, but at a point X a reversal is effected between two parts of the winding, by means of reversing the connections of the right-hand smaller portion of the winding. That is, in Fig. 2 the winding is interrupted at the end of the/f right-hand larger portion and at the lefthand end of the smaller portion, the two portions being connected by thelead X extending from the right-hand end of the lefthand portionlto the right-hand end of the right-hand portion,-the lead to the plate battery being taken from the left-hand end of the right-hand portion. The met-hed in Fig. 2 is that obtained by means of connections to primary PR itself, whereas the method of Figs. l and 2 is effected by means of a reversal in -the winding of primary PR itself. The effectof either method is that the magnetic flux due to current in one portion of the winding is opposed to the magnet-ic flux due to the same current in another portion of the winding. All this is involved in the problem of providing the damping necessary in amplifiers of this type for the purpose of preventing undesirable oscillations in the amplifier circuits. By thus opposing the magnetic fluxes in different parts of the transformer winding, it is possible by the above means to obtain adequate damping by resistance of the wire of the winding without the necessity of using such fine wire as to be mechanically unsatisfactory. The opposition of magnetic fluxes permits increase to such extent of the length of the winding without producing an undue net amount of inductance in the circuits, as to provide the necessary damping by way of resistance of the increased length ofwire in lieu of the resistance heretofore provided by a wire of such small diameter as to be liable to breakage on account of weak structure of the wire. The direct effect of the opposition of parts of the winding and resultant opposition of magnetic fluxes is of course to decrease the effective inductance of the coil, which would be unduly increased if attempt were made to remedy the mechanical defects of line wire by simply using a greater length of wire of larger diameter. Nicrome wire of a diameter of three mils, and well insulated, is suitable, and, notwithstanding its very large diameter relative to that heretofore used for this purpose, provides the necessary damping resistance on account of the greater length pennitted by the feature of reducing the inductance for such greater length by the reversal of magnetic fluxes.

In a multi-stage tube amplifier such as is shown in Fig. 3, the damping conditions are improved also by the following construction. The insulating sheet VIS of the transformer of Fig. l is extended from end to end of the set as shown in Fig. 3, and the cores IL of each of the transformers are mounted on this extended supporting sheet- IS, which then is common to all the transformers of Fig. 3. This construction is made variable for wave'lengtl adjustment by movement to left or right, effected by rack and pinion arrangement on a wave length indicator shown at the right in Fig. 3, so that the cores IL may be moved axially in and out of their respective transformers. Then the core is directly within its coils, in the case of each transformer, the transformer windings have maximum industance because of the increased permeability of the space inside the winding for the magnetic flux of the winding, such increased permeability being due to the presence of the iron core inside the winding. lVhen the core is moved away from its position wholly within its windings, the inductance of the winding is reduced. lVhen the core is inside the winding, therefore, the transformer is adapted for the higher wave lengths, and as the core is moved out of its windings, the transformer is adapted for the lower wave lengths due to the reduced inductance of the windings. In connection with these movable cores, there are provided a corresponding number of copper tubes CT, which are secured to insulating supporting sheet IS, as, for example, by pins C and insulating disks D (Fig. 3). These copper tubes are mounted adjacent cores IL, so that they directly follow the movements of the cores and compensate therefore in the following manner. As the core leaves its position inside its coils, copper tube CT begins to enter inside the coils in place of the core, and acts as a shortcircuiting turn, thereby decreasing the inductance of the transformer winding below what it would be if air alone were left to take the place of iron core IL. Thus the entrance of copper tube GT acts to decrease the inductance of the winding and adapt it for the lower wave lengths. This action of the copper tube as a short-circuiting winding is due to its closed or tubular nature analogous to a .single turn of a short-circuiting winding. rl'he thickness of the tube depends upon the frequency of the currents employed, being only a few mils thick at radio frequencies. Tubes CT also have the elect of increasing the damping of the transformer winding, thereby compensating for the loss lll) `of desirable damping by the Withdrawal of iron cores` IL. 'Ihese variably positioned cores IL -with their compensating copper tubes T per-mit shifting of the wave length range of the entire amplifier. In practice, they have been used to shift the Wave length of the set satisfactorily from optimum operation at three hundred meters (when cores IL are nearly completely withdrawn from their'coils) to optimum operation at four hundred meters (when cores IL lie entirely within their coils). In Fig. 3, the input tothe amplifier is diagrammatically indicated at the left at coil I, the output being at the telephones PH at the right.

In Figs. 1, 2 and 2a, the longer or lefthand portion of primary PR is shown as connected to the plate of the tube. This is because this connection has been found to give the best results, although the reason is not clear. The winding is entirely operative, however, ifthe" tube platebe connected to the smaller or right-hand portion of 'primary PR, i. e., to the right of reversal point X.

In Figs. 4 and 5 is shown a perfected form of construction of transformers ein! c of the varnished paper sheet construction yof Fig. 1) an insulating form IF is provided for use in connection with separate coils termed pies oi'l pancakes shown in Fig. 5. Form IF of Fig. 4 is a structure consisting of suitable insulating material fabricated to the shape shown, to leave annular slots for the reception of the pies for the primary and secondary windings. Form IFlniay, for example, be bakelite turned out in a lathe; but I piefer to mold forni IF out of insulating material, such asgany, of the moldable materials on the market, including the shellac or bakelite class of moldable compounds. In Fig. 4, for` example, the first slot at the left of form IF (Fig. 4) is filled with a pancake or pie coil PA (Fig. 5) constituting one of the seven pies of the primary winding. The second slot in form f IF isl filled by a secondary pie SA, constituting one of the seven pies of the secondary winding. The remaining slots of form IF are filled alternately with primary and secondary pies as shown.

(lne of the practical advantages of the transformer construction of Fig. 4 over that of Fig. 1 is that it permits winding of the coils independent of the laminated core IL,-the pie coils being wound in the slots of form IF and thereafter core IL with its insulating support IS being slipped into the interior of form IF. Also foim IF is `interiorly shaped to confoi'in to the rectience with core IL. The opposition' of inagnetic'fluxes in the transformer construction y `versal point X (Figs.-.\4, 4aN 'and 5) the remaining two pies' of the-.primary (PF and PG) are wound anticlockwise, so that a straight connection between pies PE and, PF, i. e., Without any reverse connection, will cause an opposition of magnetic fiuxes between the first five and`tlie second two pies. In this case, as in the form of Figs. 1, 2 and 2a, a much greater length of wire may be used without exceeding the desired wave length, and consequently a relatively large, strong Wire can be employed for the primary winding. Heretofore it has been necessary in many cases (in order to provide the desired resistance damping) to use a nicrome wire as small as .0015 inch in diameter. By employing my methods, an ordinary commercial copper or niclirome wire of .several mils diameter canfbe employed, without materially reducing the deduring) lmanufacture, but -resulted frequently (in the use of the transformer) in breakage of the fine wire by mechanical jarrings of the set, thereby putting the latter out of operation. As aI comparative example, a primary of a prior tube radio frequency amplifier transformer, consisting of nicrome wire .0015 inch in diameter and 12 feet long wound in 80 turns, may be replaced according to this feature of my invention by a primary of`- nichroine wire .003 inch in dianieteiand 35 feet long.

The transformers of Figs. 1 or 4 may be employed in'eit-her of the sets diagramma-tically shown in Fig. 3, or in any other tube set where transformers are employed. These sets will be understood from the drawings, being of ordinary present construction and arrangement sa-ve for my improvements hereof. In Fig. 8 is shown a four-tube set in which the first three tubes are radio frequency amplifiers (RF1, RF2 and PtF), and the fourth tube is a detector P. In Fig. 6 is shown a six-tube-'set in Which the vfirst three tubes are radio frequency amplifiers, the fourth tube is a detector I), and the remaining two tubes are audio frequency amplifiers supplying the telephones PH.`

My improvements are most useful as the` radio frequency transformers of these sets (RTl, RT2 and RTB). As to the opposition of magnetic fluxes, this is most useful in the primary winding alone, as shown in Figs. l and .4, although i-t may be employed in the secondary alone, or in both primary and secondary, as will be illustrated.

In Fig. 6 is shown another form of transformer similar to that of Fig. l, but with the primary wound with a plurality of reversals at the successive pomts of reversal X. At the left is a. portion of seven turns, then a point X of reversal, and then a smaller portion of three turns before the next point of reversal X; and these portions are alternately of large and small portions, comprising seven portions as shown, four of which are large and three of which are small; but as in Fig. l, one ot' the larger portions is connected to the plate of the tube. In a long winding, this provision of a larger number of reversed portions ensures the desired action ot opposition of magnetic fluxes throughout the primar PR. It is believed that this transformer glves better all-around results than the forms ot' Figs. 1 and 4 where the primary isdivided into only two reversed portions. In the transformers of Figs. 4 and G, insulating supporting sheet IS may be mechanically extended to support a plurality of cores as shown in Fig. 3. In no case, however, need the sheet IS be insulating throughout its length, for, on the contrary, it may be' mechanically strengthcned by metal supports at portions of its length intermediate pairs of a core IL and a copper tube CT, being supported in any event in bearings B, Fig. 3, through which it can slide as actuated by the rack and pinion arrangement shown at the right. The right-hand rack portion, ot' course, is preferably of metal, mechanically connected to insulating portion of support IS.

In Fig. 7 is shown the method of obtaining the opposed portions of primary PR of Fig. 6 which is by the winding method illustrated in Figs 2 and 4a. In Fig. 4n the pies are omitted from form IF for elearness, but thel connections are shown, and they correspond with those of Fig. 5, the coils being shown in Fig. 5 for clearness in view of their omission from Fig. 4a. Fig. 7 shows the method applied to Fig. 6 so clearly as not to require special description. In Fig. 7 is shownl the reverse connection method applied to the transformer of Fig. G.

In Figs. 8 and 8il is shown a form of my transformer construction wherein the entire winding is divided (as to reversed portions) into three equal portions, instead of two unequal portions as in Figs l and 4, and of a plurality of unequal portions as in Fig. 6. In Figs. 8 and 8a there are the. same munber of turns in each portion. This is a convenience in manufacture and provides a symmetrical form of transformer. This is believed to be anadvantageous alternative embodiment of the invention. The method of obtaining the opposition of qnagnetic fluxes is shown in Fig. 8 as by winding (the method shown in Figs. 2, 4u and 7) and the method shown in Fig. 8a is the method by connection (the method shown in Figs. 2 and 7a).

In Fig. 9 is shown one of my amplifier transformers wherein the method of opposition of magnetic fluxes is ellected-in both primary and secondary. In Fie, 9, the heavier lines represent primary PR and the lighter lines represent secondary SG. For clear-ness, the windings are shown without their support. or core as in the case of other figures. In Fig. 9 the opposition of fluxes obtained by the winding method, the lefthand portions of each ot' the primary and secondary being wound say clockwise, the middle,portions say anticlockwise, and the right-hand port-ions clockwise, these portions commencing at the points of reversal X. In Fig. 9 the three portions areA indicated as being equal of synnnetrical as in Figs. 8 and S. The form of Fig. 9 is believed to be advantageous for use in some casesV such as those requiring increased damping in the secondary to provide for an increase of damping in the grid circuit ot' the succeeding tube to which the secondary is connected (see Figs. 3 and G).

As to the above descriptions and diagrams of the flux-opposing arrangements, it will be understood, ot' course, that the directions are ii'istantaneously relative, for the currents employed are oscillating currents such that the direction of current ilow throughout any of the forms of transformers is reversed at cach alternation of the oscillating current.

I claim l. The improved oscillation damping` co1lpli11g-transtormer system, which comprises a plurality ol' transformers each having windings possessing inductance and resistance for desired wave-length and damping ot' its circuits, and a core movable out wardly and inwardly of its said windings; means varying the wave-lengths of the circuits of lthe transformers by simultaneous movement of the several cores; at least one of the windings of each ot' the transformers having electrically'opposed portionsl causing opposing magnetic lluxes permitting the desired damping of the system by the relsistance of the wire ol such winding without unduly increasing the length and effective -inductance and wave-length o such winding; and a plurality of short-circuiting devices ref-tpeetively mounted adjacent to and movable with the several cores thereby moving inwardly of the windings as the cores are moved outwardly and compensating for the loss of desirable damping of the transformer circuits by the outward core movements.

2. A circuit-damping transformer for coupling tuned oscillatory circuits, which comprises a core, and a movable support therefor permitting movementof the core outwardly of the transformer windings and varying the wave-length of the transformer; the wimlings havingresistance for desired damping otl their circuits; and a short-circuiting device also mounted on the said coresupport adjacent the core thereon permitting movement of said device inwardly of the windings as the core is moved outwardly and thereby compensating for the loss of desirable damping of the transformer by the outward core movement.

3. A c iremt-damping transformer for tuned oscillatory circuits, which comprises a core and a movable support therefor, and windings having induct'ance and resistance for desired wave-length and damping of their circuits; at least one of the windings comprising electrically` opposed portions causing opposing magnetic fluxes which permit the desired damping by the resistance of the wire of the winding without unduly increasing the effective induetance and wave-length of such winding; and a shortcireuiting device mounted on thel core-support adjacent the core thereon and movable inwardly of the transformer windings as the core is moved outwardly, compensating for the loss of desirable transformer damping by the outward core movements.

4. The improved oscillation damping coupling transformer system, which comprises a plurality of transformers each having windings possessing inductance and resistance for desired wave-length and damping of their circuits and a core movable ontwardly of the windings; said transformers each having at least one of its windings consisting otl electrically opposed portions causing opposing magnetic tluxes permitting the desired damping by the resistance ot' the wire of the winding without substantially varying the effective induct'ance and wavelength; and means varying the wave-lengths ot' the transformer circuits by simultaneous movement of the several cores.

5. The improved oscillation damping eoupling transformer system, which comprises a plurality of transformers provided with windings having iiuluetance and resistance for desired wave-length and damping ot their Circuits and with a core movable out'- wardly and inwardly oli its said windings; means varying the wave-lengths ot' the transformer circuits by simultaneous movements of said several cores; and a plurality of short-eireuiting devices respectively mounted adjacent to and movable with the several cores thereby moving inwardly of the windings as the cores mo've outwardly and compensating for tbe loss of desirable damping of the system by the outward core movements.

VILLIAM M. BAILEY. 

